GMaps

GMaps allow you to see a run on satellite and calculate the distance.  You can easily zoom in and double click a starting point and then double click an ending point.  GMaps then draws a line between the two points and you may then double click another point and continue to do so thus drawing lines to map out your run.  Start by clicking the Maps icon in the upper right corner so that it is easy to search for the general area of the location you want to map then click Satellite to view and map it.  There's plenty of help and instructions at the site.

Here's the site: http://www.gmap-pedometer.com/

Here's a map of the track at Westlake: http://www.gmap-pedometer.com/?r=1168850

Here's Chesebro Canyon:  I mapped about the first half mile but it's quite simple to zoom in and map as far out as you like: http://www.gmap-pedometer.com/?r=1168876